Ethernet is basically a broadcast protocol. Its main advantage is its simplicity. This allows Ethernet to be implemented with less costly hardware and software. Ethernet has become a common protocol for local area networks. For purposes of this application, the term “Ethernet” includes the entire class of Carrier Sense Multiole Access/Collision Detection (CSMA/CD) protocols covered by the family of computer industry standards known variously as IEEE-802.3 and ISO 8802/3. This includes but is not limited to 1-Mb Ethernet, known as “StarLAN”, 10-Mb Ethernet, 100-Mb Ethernet, known as “Fast Ethernet”, 1-Gb Ethernet and any future CSMA/CD protocols at any other data rates.
Ethernet, as with other network protocols, transmits data across a packet switched network. In packet switched networks data is divided into small pieces called packets that can be multiplexed onto high capacity inter-machine connections. Packet switching is used by virtually all computer interconnections because of its efficiency in data transmissions. Packet switched networks use bandwidth on a circuit as needed, allowing other transmissions to pass through the lines in the interim.
A packet is a block of data together with appropriate identification information necessary for routing and delivery to its destination. The packet includes a source address, a destination address, the data being transmitted, and a series of data integrity bits commonly referred to as a cyclical redundancy check or CRC. The source address identifies a device that originated the packet and the destination address identifies a device to which the packet is to be transmitted over the network.
As is known in the art transmission of a data packet on a packet switched network results in s transmission burst entails synchronously transmitting all bytes which make up the data packet. A data packet being transmitted on a 1 Gb Ethernet network has a u capacity of a certain maximum number of bytes corresponding to the network bandwidth capacity, but usually a fewer number of bytes are transmitted.
In simple point-to-point networks having only an origin node and a destination node, idle bytes can be inserted between packets. In more complex multi-node networks a link between nodes “i” and “j” is frequently left silent when there is nothing to be transmitted from node “i” to node “j”
An Ethernet packet size typically ranges from 40 to about 1500 bytes. A transmission rate of data communicated on the 1 Gb Ethernet network is typically less than about 600 Mbps; and is frequently not delay sensitive. Moreover, 1 Gb Ethernet packet transmissions are generally “bursty”— that is, they comprise a series of short, high density burst with idle bytes or silent periods dispersed between the burst.
A main drawback with conventional Ethernet is that there are significant limitations on the physical distance that the network can cover. Gigabyte Ethernet networks as with other forms of Ethernet are typically found in relatively short distance Local Area Networks (LANs) and Metropolitan Area Networks (MANs).
Long distance networks such as Wide Area Networks (WANs) frequently comprise Switched Optical Networks (SONETs) and frequently utilize conventional communications protocols such as OC12, OC3, or OC1, hereinafter collectively referred to as OCnc. In SONETs there is no particular packet size requirement.
Where it is desired to communicate the Ethernet data packet from the LAN or MAN in a first location across the long distance network to the LAN or MAN in a second location, it is necessary to convert the Ethernet packet to a format suitable for transmission across the long distance network. Encapsulation protocols have been developed to allow Ethernet packets to be transmitted over longer distances. In such protocols, the entire Ethernet packet is placed within another type of packet which has its own header and includes additional addressing information, protocol information, etc., and which conforms to a format of the long distance network. Thus, in encapsulation techniques the size of an encapsulating packet must be larger than a size of an encapsulated packet.
Currently known OC12 SONET/WAN systems have a bandwidth capacity of about 622 Mbps. On the other hand, 1 Gb Ethernet packets are, by definition, one gigabyte. Thus, in order to communicate a 1 Gb Ethernet packet on an OC12 network a technique other than simple data encapsulation is required.
The prior art includes many attempts to solve the problem of transmitting a large packet through an intervening smaller packet carrying network. This prior art includes the following U.S. patents:
U.S. Pat. Nos. 6,094,439 and 6,081,523 to Krishna et al., incorporated herein in their entirety by reference, disclose a Gigabit network node having a media access controller outputting packet data at Gigabit rates using multiple 100 MB/s physical layer links coupled to a physical interface having a data router to enable implementation of a Gigabit network using low cost data links. At least a portion of the packet data is selectively transmitted in a modified reconciliation layer onto the plurality of physical layer links.
U.S. Pat. No. 6,002,692 to Wills, incorporated herein in its entirety by reference, discloses an apparatus for interfacing a high speed broad bandwidth communication network to a communication fabric having a bandwidth which is a fraction of the high speed broad bandwidth network; and where the network and the fabric have different data packet formats. Data packets in a format of the high speed broad bandwidth network are converted to data packets in a format of the communications fabric and transmitted therethrough. At a terminal end of the fabric the data packets in the format of the fabric are re-converted back to the format of the high speed broad bandwidth network.
U.S. Pat. No. 5,751,723 to Vanden Heuvel et al., incorporated herein in its entirety by reference, discloses an apparatus and method for recovery of bandwidth overhead in a a packetized network wherein a secondary information is interleaved into vacant or idle bytes in a data packet having a primary information.
U.S. Pat. No. 5,687,176 to Wisniewski et al., incorporated herein in its entirety by reference, discloses an apparatus and method for zero-byte substitution in a channel unit or line card coupling a digital subscriber Lein to a digital transmission facility. An occurrence of an all-zero data byte causes a corresponding zero byte indicator flag to be produced, and also causes the all-zero byte to be replaced by the preceding non-zero data byte rather than by a prescribed or predetermined data byte. On the receive side, the occurrence of a repeated data byte is detected and causes the current data byte to be replaced by an all-zero byte to restore the original data.
U.S. Pat. No. 5,583,863 to Darr, Jr. et al., incorporated herein in its entirety by reference, discloses an arrangement for transporting digital broadband data output in Asynchronous Transfer Mode (ATM) cell streams from a plurality of video information service providers (VIPs) to a plurality of subscribers. A digital broadband network is adapted to receive a plurality of ATM streams from VIPs via optical fibers having a predetermined capacity. A plurality of receivers corresponding to the optical fibers output ATM cells from the optical fibers having active ATM cell streams to an ATM edge device having input ports corresponding to the Ln predetermined capacity of the optical fibers. The ATM edge device grooms the ATM cells by rejecting unauthorized cells and idle cells that do not carry information, and maps the remaining ATM cells to output ports having a lower predetermined capacity than the plurality of optical fibers coupled to the receivers. The mapped ATM cells are assigned translated VPI/VC: identifiers and are combined onto common signal paths for transport via optical fibers.
U.S. Pat. No. 5,371,547 to Siracusa et al., incorporated herein in its entirety by reference, discloses an apparatus for excising specific data from a data stream to reduce its transmission bandwidth; and for re-inserting the excised data to regenerate the original data stream.
U.S. Pat. No. 5,020,058 to Holden et al., incorporated herein in its entirety by reference, discloses a data communication system having a repetitive pattern packet suppression technique which suppresses transmission of entire packets in a data stream when a repeating pattern has been established in the previous packet and is then found to repeat throughout the following packets. The resulting hole in the data stream is filled at a destination end with the last pattern from the previously received packet.
Other U.S. patents of interest include: U.S. Pat. No. 6,157,637 to Galand et al.; U.S. Pat. No. 6,154,462 to Coden; U.S. Pat. No. 6,148,010 to Sutton et al.; U.S. Pat. No. 6,111,897 to Moon; U.S. Pat. No. 6,088,827 to Rao; U.S. Pat. No. 6,088,369 to Dabecki et al.; U.S. Pat. No. 6,014,708 to Klish; U.S. Pat. No. 5,999,525 to Krishnaswamy; U.S. Pat. No. 5,970,067 to Sathe et al.; U.S. Pat. No. 5,680,400 to York; U.S. Pat. No. 5,570,356 to Finney et al.; U.S. Pat. No. 5,293,378 to Shimizu; and U.S. Pat. No. 4,796,254 to van Baardwijk et al.; each of which is incorporated herein in its entirety by reference.
In spite of the numerous existing or published patents, there remains a need for a system that can reliably, economically and efficiently take a data packet for a larger bandwidth network and compress it to a size such that it can be transmitted on a narrower bandwidth.